Editing Idiopathic intracranial hypertension (section)

==Diagnosis==
[[File:UOTW 5 - Ultrasound of the Week 2 (cropped).jpg|thumb|upright=1.3|Ultrasound of the optic nerve showing IIH<ref name=UOTW5>{{cite web|title=UOTW #5 - Ultrasound of the Week|url=https://www.ultrasoundoftheweek.com/uotw-5/|website=Ultrasound of the Week|access-date=27 May 2017|date=17 June 2014}}</ref>]]
The diagnosis may be suspected on the basis of the history and examination. To confirm the diagnosis, as well as excluding alternative causes, several investigations are required; more investigations may be performed if the history is not typical or the person is more likely to have an alternative problem: children, men, the elderly, or women who are not overweight.<ref name=FriedmanJacobson2002/>

===Investigations===
[[Neuroimaging]], usually with [[computed tomography]] (CT/CAT) or [[magnetic resonance imaging]] (MRI), is used to exclude any mass lesions. In IIH these scans typically appear to be normal, although small or slit-like [[ventricular system|ventricles]], dilatation and buckling<ref>{{cite journal |vauthors=Tan YJ, Choo C| year = 2020 | title =Idiopathic Intracranial Hypertension – Characteristic MRI Features | journal = Headache | volume = 60 | issue = 9| pages = 267–8 | doi=10.1111/head.13931| pmid = 32757392| s2cid = 221014881 }}</ref> of the optic nerve sheaths and "[[Empty sella syndrome|empty sella sign]]" (flattening of the [[pituitary gland]] due to increased pressure) and enlargement of Meckel's caves may be seen.

An MR venogram is also performed in most cases to exclude the possibility of venous sinus stenosis/obstruction or [[cerebral venous sinus thrombosis]].<ref name=Binder/><ref name=Soler/><ref name=FriedmanJacobson2002/> A contrast-enhanced MRV (ATECO) scan has a high detection rate for abnormal transverse sinus stenoses.<ref name="Farb">{{cite journal|last1=Farb|first1=RI|last2=Vanek|first2=I|last3=Scott|first3=JN|last4=Mikulis|first4=DJ|last5=Willinsky|first5=RA|last6=Tomlinson|first6=G|last7=terBrugge|first7=KG|title=Idiopathic intracranial hypertension: the prevalence and morphology of sinovenous stenosis.|journal=Neurology|date=May 13, 2003|volume=60|issue=9|pages=1418–24|pmid=12743224|doi=10.1212/01.wnl.0000066683.34093.e2|s2cid=34459740}}</ref> These stenoses can be more adequately identified and assessed with catheter cerebral venography and manometry.<ref name=Ahmed/> Buckling of the bilateral optic nerves with increased perineural fluid is also often noted on MRI imaging.

[[Lumbar puncture]] is performed to measure the opening pressure, as well as to obtain [[cerebrospinal fluid]] (CSF) to exclude alternative diagnoses. If the opening pressure is increased, CSF may be removed for transient relief (see below).<ref name=FriedmanJacobson2002/> The CSF is examined for abnormal cells, infections, antibody levels, the [[glucose]] level, and [[protein]] levels. By definition, all of these are within their normal limits in IIH.<ref name=FriedmanJacobson2002/> Occasionally, the CSF pressure measurement may be normal despite very suggestive symptoms. This may be attributable to the fact that CSF pressure may fluctuate over the course of the normal day. If the suspicion of problems remains high, it may be necessary to perform more long-term monitoring of the ICP by a pressure catheter.<ref name=FriedmanJacobson2002/>

===Classification===
The original criteria for IIH were described by [[Walter Dandy|Dandy]] in 1937.<ref name=Dandy1937>{{cite journal |author=Dandy WE|date=October 1937 |title=Intracranial pressure without brain tumor - diagnosis and treatment |journal= Annals of Surgery |volume=106 |issue= 4|pages=492–513 |pmc=1390605 | doi = 10.1097/00000658-193710000-00002|pmid=17857053}}</ref>
<!--Keep whitespace below, as table gets bunched only next paragraph-->
{| border="1" align="center" style="text-align: center; background: #FFFFFF;"
|+ Dandy criteria<ref name=Dandy1937/>
|-bgcolor="#EFEFEF"
| 1	Signs & symptoms of increased ICP – CSF pressure >25 cmH<sub>2</sub>O
|-bgcolor="#EFEFEF"
| 2	No localizing signs with the exception of abducens nerve palsy
|-bgcolor="#EFEFEF"
| 3	Normal CSF composition
|-bgcolor="#EFEFEF"
| 4	Normal to small (slit) ventricles on imaging with no intracranial mass
|}

They were modified by Smith in 1985 to become the "modified Dandy criteria". Smith included the use of more advanced imaging: Dandy had required [[Cerebral ventriculography|ventriculography]], but Smith replaced this with [[computed tomography]].<ref name=JLSmith>{{cite journal |author=Smith JL |title=Whence pseudotumor cerebri? |journal=Journal of Clinical Neuroophthalmology |volume=5 |issue=1 |pages=55–6 |year=1985 |pmid=3156890}}</ref> In a 2001 paper, Digre and Corbett amended Dandy's criteria further. They added the requirement that the person is awake and alert, as coma precludes adequate neurological assessment, and require exclusion of venous sinus thrombosis as an underlying cause. Furthermore, they added the requirement that no other cause for the raised ICP is found.<ref name=Binder/><ref name=Acheson/><ref name=DigreCorbett>{{cite journal |vauthors=Digre KB, Corbett JJ | title=Idiopathic intracranial hypertension (pseudotumor cerebri): A reappraisal | journal=Neurologist | year=2001 | volume=7 | pages=2–67 | doi=10.1097/00127893-200107010-00002}}</ref>
<!--Keep whitespace below, as table gets bunched only next paragraph-->
{| border="1" align="center" style="text-align: center; background: #FFFFFF;"
|+ Modified Dandy criteria<ref name=DigreCorbett/>
|-bgcolor="#EFEFEF"
| 1	Symptoms of raised intracranial pressure (headache, nausea, vomiting, transient visual obscurations, or papilledema)
|-bgcolor="#EFEFEF"
| 2	No localizing signs with the exception of abducens (sixth) nerve palsy
|-bgcolor="#EFEFEF"
| 3	The patient is awake and alert
|-bgcolor="#EFEFEF"
| 4	Normal CT/MRI findings without evidence of thrombosis
|-bgcolor="#EFEFEF"
| 5	LP opening pressure of >25 cmH<sub>2</sub>O and normal biochemical and cytological composition of CSF
|-bgcolor="#EFEFEF"
| 6	No other explanation for the raised intracranial pressure
|}

In a 2002 review, Friedman and Jacobson propose an alternative set of criteria, derived from Smith's. These require the absence of symptoms that could not be explained by a diagnosis of IIH, but do not require the actual presence of any symptoms (such as headache) attributable to IIH. These criteria also require that the lumbar puncture is performed with the person lying sideways, as a lumbar puncture performed in the upright sitting position can lead to artificially high pressure measurements. Friedman and Jacobson also do not insist on MR venography for every person; rather, this is only required in atypical cases (see "diagnosis" above).<ref name=FriedmanJacobson2002/>